1. Field of the Invention
The present invention relates to a method for cutting a liquid crystal display panel and more particularly, to a method for cutting a liquid crystal panel to cut a plurality of liquid crystal display panel formed on large-scale mother substrates into a plurality of unit liquid crystal display panels, and a method for fabricating a liquid crystal display panel using the same.
2. Discussion of the Related Art
As consumer interest in information displays has grown and the demand for portable (mobile) information devices has increased, research and commercialization of light and thin flat panel displays (“FPD”) has also increased. Flat panel displays may be substituted for a Cathode Ray Tube (“CRT”), which is the most common existing display device.
The liquid crystal display (“LCD”) is a FPD device for displaying images by using optical anisotropy of liquid crystal. LCD devices exhibit excellent resolution and color and picture quality and as a result are widely employed in notebook computers, desktop monitors, and the like.
The typical LCD device includes a liquid crystal display panel including a driving circuit unit, a backlight unit installed at a lower portion of the liquid crystal display panel and emitting light to the liquid crystal display panel, a mold frame for supporting the backlight unit and the liquid crystal display panel, and a case.
As illustrated in FIG. 1, the liquid crystal display panel 10 includes an image display part 13 in which liquid crystal cells are arranged in a matrix form, a gate pad part 14 connected to gate lines 16 of the image display part 13 and a data pad part 15 connected to data lines 17 of the image display part 13.
The gate pad part 14 and the data pad part 15 are formed at an edge region of a thin film transistor (TFT) array substrate that does not overlap with a color filter substrate 2. The gate pad part 14 supplies scan signals provided from a gate driver (not shown) to the gate lines 16 of the image display part 13, and the data pad part 15 supplies image information provided from a data driver (not shown) to the data lines 17 of the image display part 13.
Although not shown, the color filter substrate 2 includes a color filter including red, green and blue sub-color filters implementing colors, a black matrix for separating the sub-color filters and blocking light from transmitting through a liquid crystal layer, and a transparent common electrode for applying a voltage to the liquid crystal layer.
The array substrate 1 includes a plurality of gate lines 16 and a plurality of data lines 17 arranged vertically and horizontally thereon and defining a plurality of pixel regions; a TFT to be used as a switching element formed at each crossing of the gate lines 16 and the data lines 17; and a pixel electrode formed on each pixel region.
The array substrate 1 and the color filter substrate 2 face each other and are bonded together manner by a seal pattern 40 formed at an edge of the image display part 13 to form a liquid crystal display panel 10. The attachment of the two substrates 1 and 2 with the proper alignment is facilitated through an alignment key (not shown) formed on one of the array substrate 1 and the color filter substrate 2.
To improve manufacturing yield the TFT array substrates are formed on a large-scale mother substrate while the color filter substrates are formed on a separate mother substrate. The two mother substrates are then bonded together facing each other to form a plurality of liquid crystal display panels. A cutting process is performed to cut the bonded mother substrates into a plurality of unit liquid crystal display panels.
Typically, cutting of the mother substrates is performed by forming a prearranged cut line on the mother substrates using a wheel having a hardness greater than that of glass and then forming and propagating a crack along the prearranged cut line.
FIG. 2 is a view showing the structure of a section of the unit liquid crystal display panel formed by attaching the first mother substrate on which the TFT array substrates are formed to the second mother substrate on which the color filter substrates are formed.
As shown in FIG. 2, in the unit liquid crystal panels, the thin film transistor array substrates 1 protrude at one side beyond the color filter substrates 2, because the gate pad part and the data pad part are formed at an edge portion of the thin film transistor array substrate 1 that does not overlap the color filter substrate 2.
Accordingly, the color filter substrates 2 formed on the second mother substrate 30 are separated by first dummy regions 31 each having a width corresponding to the protruding portion of the thin film transistor array substrates 1 formed on the first mother substrate 20.
The unit liquid crystal panels are typically disposed such that the first and the second mother substrates 20 and 30 can be utilized to their maximum, and though the arrangement differs depending on a model of the unit liquid crystal display panel, the unit liquid crystal panels are typically formed to be separated by the width of a second dummy region 32.
After the first mother substrate 20 having the thin film transistor array substrates 1 formed thereon and the second mother substrate 30 having the color filter substrates 2 formed thereon are attached, the substrates are cut into individual liquid crystal panels. During the cutting process, the first dummy region 31 formed at the portion where the color filter substrates 2 of the second mother substrate 30 are separated and the second dummy region 32 separating the unit liquid crystal panels are simultaneously removed.
A related art cutting process for manufacturing the liquid crystal display panel will be described hereinafter with reference to FIG. 3.
FIG. 3 is a view showing a cutting process of the liquid crystal display panel of the related art.
As shown, a cutting device of the liquid crystal display panel includes a table 42 on which the bonded first and second mother substrates 20 and 30 are loaded, and a cutting wheel 55 for processing the first and second mother substrates 20 and 30 to form prearranged cut lines 51.
When using the cutting device of the related art, after the bonded first and second mother substrates 20 and 30 having a plurality of liquid crystal display panels are loaded on the table 42, the cutting wheel 55 positioned at an upper side of the first and second mother substrates 20 and 30 is lowered and rotated to apply a certain pressure against the second mother substrate 30 to form prearranged cut lines 51 or grooves on the surface of the second mother substrate 30.
The prearranged cut lines are also formed on the first mother substrate 20. The first mother substrate 20 is processed with the cutting wheel 55 to form prearranged cut lines at the same positions as the prearranged cut lines 51 of the second mother substrate 30. Accordingly, in the liquid crystal panel cutting process of the related art, since the first and second mother substrates 20 and 30 are to be processed to form corresponding prearranged cut lines, after the second mother substrate 30 is processed with the cutting wheel 55, the liquid crystal panel is reversed to have the first mother substrate 20 face upward and the first mother substrate 20 is processed with the cutting wheel 55.
Thereafter, pressure is applied to the prearranged cut lines 51 formed on the first and second mother substrates 20 and 30 to separate the first and second mother substrates 20 and 30 along the prearranged cut lines 51. The first and second mother substrates 20 and 30 are separated by striking the first and second mother substrates 20 and 30 with a breaking bar to make and propagate a crack along the prearranged cut lines 51.
In cutting the liquid crystal display panel, a scribing process and a breaking process are performed several times through a plurality of reversals and positionings of the substrates 20 and 30. The significant amount of time used for the scribing process and the breaking process reduces productivity of the overall manufacturing process.
In addition since the mother substrates are struck with the breaking bar to make cracks along the prearranged cut lines formed on the mother substrates, a plurality of glass chips are generated. Further, if the striking is performed inaccurately or if crack propagation is incomplete, the liquid crystal display panel may be damaged or torn off when it is extracted.